Note he said >can< severely damage your career and mental health, not >will< severely damage your career and mental health.
The former implies a possibility. That what he describes didn't happen in your case, while worth applauding, doesn't make the possibility any less true, especially for those that actually experience what the OP describes.
That's exactly the part that bothers me the most. It's just like fortune tellers saying what can happen. If it's a statement, then it's unfalcifiable and hence is useless. If it's something else(a lesson?) then it should have a better context. I'm just a bit strict on people making statements.
The former implies a possibility. That what he describes didn't happen in your case, while worth applauding, doesn't make the possibility any less true, especially for those that actually experience what the OP describes.